Ultra-high vacuum is a vacuum regime characterized by pressures lower than 10−7 pascal (10−9 mbar, approximately 10−9 tor). Ion pumps are used in some settings to establish an ultra-high vacuum. In an ion pump, an array of cylindrical anode tubes are arranged between two cathode plates such that the openings of each tube faces one of the cathode plates. An electrical potential is applied between the anode and the cathode. At the same time, magnets on opposite sides of the cathode plates generate a magnetic field that is aligned with the axes of the anode cylinders.
The ion pump operates by trapping electrons within the cylindrical anodes through a combination of the electrical potential and the magnetic field. When a gas molecule drifts into one of the anodes, the trapped electrons strike the molecule causing the molecule to ionize. The resulting positively charged ion is accelerated by the electrical potential between the anode and the cathode toward one of the cathode plates leaving the stripped electron(s) in the cylindrical anode to be used for further ionization of other gas molecules. The positively charged ion is eventually trapped by the cathode and is thereby removed from the evacuated space. Typically, the positively charged ion is trapped through a sputtering event in which the positively charged ion causes material from the cathode to be sputtered into the vacuum chamber of the pump. This sputtered material coats surfaces within the pump and acts to trap additional particles moving within the pump. Thus, it is desirable to maximize the amount of sputtered material.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.